New HIV vaccine trial begins in South Africa

Atlantis finally touches down in California

After NASA delayed its landing several times due to bad weather, the US space shuttle Atlantis, back from a successful mission to service the Hubble telescope, successfully touched down at the Edwards Air Force base in California on Sunday.

AFP - The space shuttle Atlantis touched down at its alternative landing spot in Calfornia Sunday after a successful mission to repair and upgrade the Hubble Telescope.

After 12 days, 21 hours and 37 minutes in flight, the shuttle, with its crew of seven astronauts, landed at this air base 160 km (100 miles) northeast of Los Angeles.

"Congratulations on a very successful mission giving Hubble a new set of eyes that will continue to expand our knowledge of the universe," mission control in Houston said, welcoming back the crew.

"It was a thrill, from start to finish. We had a great ride," said co-captain Gregory Johnson.

Bad weather and crosswinds pushed back Florida landing tries for three days before NASA opted for the California landing. The craft had enough fuel and supplies to be aloft until Monday at the latest.

Atlantis blasted off on May 11 with a crew of seven astronauts on what was scheduled to be an 11-day mission to repair the Hubble space telescope and extend its range and life for another five years.

NASA earlier had scrubbed a planned first attempt to land Atlantis at its home base in Florida on Sunday.

With storms not too far from the Florida space center, the Houston, Texas, control center asked the seven astronauts to take another whirl around Earth hoping weather conditions improve in Florida ahead of another try.

But as things failed to look clear enough for a Florida green-light, the California landing was set.

NASA prefers to bring it down in Florida to save the two million dollars it costs to move the shuttle back to base in Florida.

Under NASA rules, a decision on whether to attempt a landing has to be made one hour and a half hours before the planned touchdown. Once the crew begins its descent toward Earth, the decision cannot be reversed because the shuttle lacks engine power that would allow it to regain altitude.

NASA has set several conditions for a landing: the cloud cover in the skies must not be more than 50 percent, visibility must be at least eight kilometers (five miles) and lateral winds must not be blowing at more than 28 kilometers an hour (17 miles an hour).

As early as Thursday, the astronauts were told by NASA to shut down some of the computers on board the shuttle to conserve electricity in the event that their landing was delayed.

The Hubble observatory was released on Tuesday after five obstacle-filled spacewalks.

The enhancements have equipped Hubble to search for the earliest galaxies, probe the mysteries of dark matter and dark energy as well as study planet-making processes.

But the trouble was well worthwhile.

John Grunsfeld, an astronomer turned astronaut who led three of the mission's five spacewalks, told lawmakers Thursday that Hubble "is probably the most significant science instrument of all times."

As NASA struggled with the Atlantis landing, the White House announced Saturday that President Barack Obama had nominated former astronaut Charles Bolden to be the agency's new administrator.

If confirmed, Bolden would be the first African American to lead NASA and only the second astronaut.

A retired Marine Corps major general, Bolden made four shuttle voyages during his years as an astronaut and piloted the shuttle Discovery when it deployed Hubble into orbit in 1990.